1. Technical Field of the Invention
The present invention is related to methods and apparatus for handling flows of exhaust gases from reaction chambers, and more particularly exhaust gases that are laden with powder particles and that include condensable components.
2. State of the Prior Art
Many industrial processes form solid, powdery, by-products and, at the same time, involve flowing and controlling flows of effluents of the processes. For example, in a variety of chemical vapor deposition (CVD) processes, gaseous chemicals/precursors are fed into vacuum reaction chambers, where they are reacted to deposit solid films or coatings of compounds or elemental materials onto substrates. Some of such CVD processes produce solid powdery by-products, and exhausts of such powdery by-products can be problematic in exhaust pipes (often called vacuum pumping lines and sometimes called forelines in vacuum CVD systems), valves, vacuum pumps, and other flow handling components and equipment downstream from the reaction chambers, particularly when the vacuum in the process chamber is relatively low, i.e., the process pressure is relatively high, for CVD processes (e.g., in the 10 to 800 torr range), where gas phase reactions are dominant because of a short mean free path between gas molecules. Other deposition processes may exhaust unreacted gases from deposition chambers that then react downstream to form solid or liquid build-ups the in vacuum pumping lines, valves, pumps, and other components or equipment.
A variety of methods and equipment have been developed to prevent or at least minimize such solid build-up in downstream exhaust components from condensation or chemical reactions, which have been effective to various degrees. For example, pipe heaters, such as those shown and described in U.S. Pat. No. 5,714,738, issued Feb. 3, 1998, can be used to maintain higher temperatures in vacuum pumping lines and other pipes to prevent or minimize condensation. Such heaters in special forms can be used to heat at least portions of valves, vacuum pumping line, and other equipment, as shown, for example, on a an isolation valve in U.S. Pat. No. 8,196,893, issued Jun. 12, 2012. Nozzle assemblies, such as the assembly shown and described in U.S. Pat. No. 5,827,370, issued Oct. 27, 1998, can be used to create a laminar flow of inert or non-reactive gas along the inner surface of a vacuum pumping line or other pipe to prevent surface reactions of gaseous chemicals from forming solid build-ups on the inner surface of the pipe. Various traps, reactors, filters, and other equipment have been developed for removing such condensable or reactive gases from exhaust flows, for example, U.S. Pat. No. 5,820,641, issued Oct. 13, 1998, U.S. Pat. No. 6,197,119, issued Mar. 6, 2001, U.S. Pat. No. 6,488,745, issued Dec. 3, 2002, and U.S. Pat. No. 7,455,720, issued Nov. 25, 2008,
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art and other examples of related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.